1. Technical Field
This invention relates generally to a device for automatically loading a container. Particularly, this invention relates to a device for loading a shipping container or the trailer portion of a tractor trailer truck.
2. Description of the Prior Art
Trailers and shipping containers represent two of the most common cargo systems used to ship goods throughout the United States and world-wide. Labor costs alone for loading these containers run into billions of dollars per year. Additionally, injuries sustained by workers loading these containers are common, and workers compensation claims and injury related costs resulting from container loading are some of the highest of any industry.
Trailers and shipping containers are commonly loaded manually. Typically, this requires that the workers enter the container and manually position each package, involving large amounts of heavy lifting and other high injury work. Additionally, this process is slow and tedious since each package must be separately loaded and stacked.
Another common method for loading trailers and shipping containers is to stack the goods on pallets and to then load these pallets into the container using a forklift or similar piece of heavy equipment. However, it is still necessary to manually stack goods on the pallets, which is an inefficient and time consuming process. Additionally, since the pallets themselves occupy valuable shipping space, the volume of goods which can be shipped per container is decreased. Furthermore, manipulation of the heavy pallets, even using a forklift, poses a risk of injury to workers.
Several methods have been developed to load individual packages into trailers or shipping containers without the need for workers to lift heavy packages or enter the trailer or shipping container. Several of the most commonly used of these include systems developed to load mailbags into trailers. Variants of these systems, using carriages and conveyor belts, are described in a series of patents to McWilliams (U.S. Pat. Nos. 3,464,572, 3,471,037, 3,474,916, 3,476,271, 3,499,551, 3,625,376, 3,651,963, 3,779,404 and 3,836,021). However, none of these devices results in precise placement of the packages and none of them are easily generalizable to the efficient loading of uniform packages into a container.
U.S. Pat. No. 5,435,690 to Binning discloses a method and apparatus for loading layers of newspaper bundles into a cart using an elevated conveyor. The invention of Binning uses retractable guides to place layers of bundles onto the cart bottom or onto previously deposited layers. The bundles are placed in the interior of the cart by removing or opening one of the cart walls.
U.S. Pat. No. 5,181,820 to Sjogren et al. discloses another method for loading newspaper bundles into vertical carts which may then be loaded into a truck cargo space. The invention of Sjogren uses a conveyor belt and a pusher to move rows of bundles onto a loading platform. Once a complete layer of bundles is formed, the layer is then moved into the cart using a fork-like elevator platform which extends through vertical slots in one side of the cart. The layers are placed one atop another until the cart is filled.
However, the inventions of Binning and Sjogren have several disadvantages that prevent them from being easily adaptable to more general loading of packages into shipping containers and trailers. Foremost among these shortcomings is that existing shipping containers and trailers are not loaded from overhead, but are instead commonly designed to be loaded lengthwise through doors situated at one end of the container. Furthermore, it is often desirable to load the container directly, without the use of carts which can themselves take up valuable cargo space.
In U.S. Pat. No. 5,201,626, Hansen discloses a method and apparatus for loading filled sacks into a cargo container. The device of Hansen includes a loading apparatus, designed to be driven into the container, to which packages are fed via a variable length conveyor belt. The packages are pushed laterally to form a row which is moved onto a delivery platform. The delivery platform then transfers the rows to an appropriate horizontal and vertical location within the container, where the rows are unloaded and placed one atop another to form a complete vertical stack. With completion of each stack, the loader described by Hansen backs out one sack length.
However, the invention of Hansen has several major disadvantages. For example, Hansen's device requires that the delivery platform complete one full movement cycle for each row of packages to be stacked, unnecessarily slowing the loading process. Furthermore, the invention of Hansen pushes the sacks from the delivery platform, allowing them to drop and decreasing the accuracy with which the packages are delivered.